APPARATUS AND METHOD FOR CONTROLLING CHARGING VOLTAGE OF IMAGE FORMING SYSTEM

摘要

PURPOSE: An apparatus and method for controlling a charging voltage of an image forming system are provided to restrain a variation in an image caused by a change of a surface potential of a photosensitive medium to obtain a uniform image. CONSTITUTION: An apparatus for controlling a charging voltage of an image forming system includes a transformer(110) having a primary coil(110a) for receiving a voltage supplied from a power supply and a secondary coil(110b) coupled to the primary coil, a switch(120) for switching on/off power supply to the primary coil, and a rectifier(140) for rectifying a voltage induced to the secondary coil. The apparatus further includes a current detector(150) for detecting current flowing through a charging roller and outputting a signal corresponding to the detected current, an A/D converter(160) for converting the signal output from the current detector into a digital signal, a pulse width modulator(130) for controlling on/off operation of the switch, and a controller(170). The controller controls the pulse width modulator to apply the first test voltage to the rectifier and determines the first reference voltage to be applied to the charging roller. In addition, the controller controls the pulse width modulator to generate the second test voltage in the rectifier, calculates a slope value according to a current variation of the charging roller with respect to the first and second test voltages and controls the pulse width modulator to apply a value obtained by adding a correction value corresponding to the slope value to the first reference value to the charging roller.